Tungsten arc lamp



June 13, 1933; E. AoYAGl ET A.' 1,913,785

` TUNGSTEN ARG LAMP Filedsept. 1o, 1931 Patented June 13, 1933 UNITED STATES PATENT OFI-'ICE EIJ' I AOYAGI, KIYOSHI ABE, AND SOZABUBO YAMAZAKI, 0F KYOT, J'APiAlSl', ASSIGNORS T0 ZAIDAN -HOJ IN AOYAGI KENKYUSHO, OF KYOTO; JAPAN, A CORPORATION QF J APAN' TUNGSTEN Anc LAMP n Application 'iled September 10, 1931, Serialv No. 562,144, and in Japan September 22, 1930.

This invention relates to improvements in a tungsten are lamp in which the glow produced between two section of a filament automatically moves towards the space -between tungsten-balls by electro-dynamic action, characterized by the fact that the two sections connected in series and inserted to an electric' circuit parallel tothe tungsten balls are automatically opened at the convtact point of the sections owing to the heat produced in the filament.

The object of the invention is to obtain a tungsten arc lamp which starts at a` lowl voltage and is of good efficiency.

The drawing shows the construction and the electric connection of a lamp according to this invention.

There is a well known lamp called tungsten arc lamp in which neon gas has been sealed in the bulb, 'and an -arc is started between tungsten balls by the heat produced owing to the discharge in neon gas at an electric pressure higher than 100 volts. According to this means a Voltage higher than 100 volts is required for starting, but after the arc is once started, the arc voltage drops to so low as less than one third, so that the electric power is wasted uneconomically.

Another known tungsten arc lamp comprises a filament which is electrically connected parallel to tungsten balls, and electric current continues to flow through the iilament even after the arc is started. The electric power spent in the filament as light is not of good eiiciency, because the voltagedrop after the arc is started becomes large due to the stabilizing resistance or inductance in the circuit and thereby the current flowing through the filament is decreased.

Still another tungsten arc lamp has been made public in the British Patentv No. 22,437 of 1914:, in which the current flowing through the filament is cut off after the arc is started. Since in this lamp, a breaker in the lament-circuit is provided independently of the arc generation, the voltage required to be applied lfor the arc generation should be high enough and the stabilizing resistance be large which results in a large heat loss.

According to the invention under consideration, these drawbacks can be avoided as yis generated between the sections. A bi metal lD which is attached to either of the elastic holders of the sections bends outwards due to rise in temperature, effected by the heat of the filament, by which the contact C automatically'opens whereby the electro-motive force between the sections reaches to themaximum value. Owin to this fact, the inert gas in the bulb is ionized bythe thermions with high velocity as well as by the spark generated when the'contalct C opens, resulting in a glow between the sections.

The result of the inventors experiments shows that this glow is displaced towards the space between the tungsten balls B by a strong electro-dynamic action due to the current and by heating of the balls, so that it becomes the arc between the balls. Thus by a combination of the apparatus which automatically opens the circuit ofthe filament, and by utilization of the electrb-dynamic l'action of the current, the arc lamp can start at a voltage lower than in the lamps alreadylknown.

In case a resistance is used to stabilize the arc it can be replaced by a transformer with a large leakage factor so .as to lower the secondary voltage if the secondary current is increased, and thereby the whole apparatus becomes very simple.

If required,lthe starting apparatus can be provided outside the bulb. In this case, the bi-metal D and the contact C above mentioned are iitted outside the bulb, and the bi-metal is heated, for instance, fby a resistance inserted by the main circuit in series.

l a proper quantity of mercury M is sealed in the bulb, its vapour is produced by heat, resulting in the mercury arc which increases ultra-violet rays.

What we claim 1s: 1. A tungsten arc lamp coinprlsing an 1nert-gas-filled envelope, at least two tungsten,

balls and a heating filament therein and connected to each ball in parallel in an electric circuit, a starting apparatus, including a thermostat which automatically opens the circuit at or near the middle part of the filament under the influence of the heat produced in said ilament, so that the glow' which is produced along the filament when the circuit is opened by the apparatus, automatically moves towards the space between the tungsten balls under the electrodynamic action due to the current. f

2. A tungsten arc lamp comprising a high pressure inert-ga-s-lilled envelope, at least two tungsten balls and a two section heating filament therein and connected to each ball in parallel in an electric circuit, a start-l ing apparatus, including two wires connected each to an end of one of said sections, and a bi-metallic member attached to one of the wires, to open the contact when the bi-metal is heated by said filament, so that the glow which is produced along the lilament when the contact is opened by the apparatus, automatically moves towards the space between the tungsten balls under the electro-dynamic action due to the current.

ln testimony whereof we have signed our names to this specification.

EIJI AOYAGL KIYOSHI ABE. SOZABURO YAMAZAKI. 

